the limestone revetment at Promontory Point since it was built, in 1937. In the summer months, the North side of the Point functions as a "rock beach." The water is shallow and the lake bottom is sand, making the North side a family friendly swimming area. On both sides of the Point, open water swimmers enter the water off the rocks and swim across the bays. Both North and South side swimming areas are marked with "Swimming Area" buoys in the summer months. In the past, open water, or distance, swimming was a source of conflict with the Chicago Park District as the legality of swimming off the Point is ambiguous. From time to time, swimmers were ticketed. Recently, however, the Chicago Park District created an officially sanctioned open water swimming area off the South side of the Point. All motorized boat traffic is prohibited inside the buoyed areas. Events Though open-water swimming continues year-round for the brave and hearty, there are spring and fall swimming events, held on weekends near the summer solstice and the autumnal equinox to celebrate the tradition and community of swimmers at the Point. The Spring Swim Around the Rocks is held each year on the Sunday following the summer solstice. The Fall Swim Around the Rocks is held each year on the Sunday preceding the autumnal equinox. These events are open and no registration is required. Spectators watch from the shore while swimmers enter the water at the South side ladders and swim around to the north side shallows, completely circumnavigating the Point. The route then reverses back to the ladders (some swimmers complete a half-course). Revetment Much of Chicago's lakefront is landfill. To protect this lakefront park land, a seawall or revetment was built by the Chicago Park District in the 1930s. This revetment consists of limestone blocks (with an average weight 2 to 4 tons) arranged in a series of “steps” leading down to the lake. These blocks are supported by a crib structure made from wooden timbers that encloses crushed rock. At the outer edge of the revetment, a series of wooden pilings, held together by a steel rail, keep the limestone blocks from tumbling into the lake. At the Point, the revetment features four steps leading down to a wide promenade. The revetment at the Point is exposed to severe wave action and had partially failed by the early 1960s.